Mapping genes that influence risk for substance dependence is a critically important research problem, one that should be approached using many methodologies. Isolated populations (IPs) have been the focus of many disease gene mapping studies, yet often, their underlying genetic structure is not well understood. This creates major limitations in understanding results and planning future research. We propose to address this in several innovative ways. Pooled DNA samples from each of several tribal and majority SE Asian and E Asian populations will be analyzed with Affymetrix 10K SNP chips, to estimate SNP population allele frequencies. Results will be used to choose ancestry informative markers (AIMs) which will be a major component of an existing project investigating the genetic basis of opiate dependence in the Hmong, an Asian Hill Tribe IP. Successful discovery of AIMs in genetically close Asian populations will allow for their use in future admixture disequilibrium mapping studies and imply the potential for many more studies of, e.g., admixed but genetically close European populations. [unreadable] [unreadable] [unreadable]